This invention relates in general to microfiche reader printers and specifically to microfiche reader printers having multiple format capabilities.
Microfiche reader printers vary in complexity. In the most simple, the operator manually moves the platen holding the microfiche to a location where the correct frame is projected in a viewing screen. A pointer may be connected to the platen, and a frame guide may be printed below the pointer so that the operator can locate desired frames easier. After the desired frame is located, the magnified image is reflected to a printer where it is printed, often on sensitized paper.
More complex reader printers have automatic addressing so that manual searching for the desired frame is eliminated. In these systems, the microfiche is inserted into the platen in a set orientation, and the machine moves the platen a specific distance from an indexing location to the desired frame. Two stepping motors, one for the x and y coordinates are employed, and the distance between frames can be translated into a number of steps for stepping motors. Many of these machines only have the capability of making a single print.
Still more complex reader printers are substantially more automated. Such machines may be programmed to copy automatically a series of frames. After the operator positions the microfiche and selects the correct printing sequence, the machine automatically moves the platen and microfiche from frame to frame and copies each frame. These machines frequently operate at high speeds and use xerographic printing to accommodate the higher speeds.
A number of problems have been recognized in reader printers, and it is an object of the present invention to disclose and provide solutions to the problems. The first relates to multiple formats. If a reader printer is owned by a document storage company, its customers may store data on microfiches of different formats. Even a single company may use different formats for data of different sizes.
Microfiche is generally of standard size 148.75 mm (5.86 in).times.105 mm (4.13 in), but microfiche is produced in nine different formats standardized by the National Microfilm Association. The following seven formats are most frequently used.
__________________________________________________________________________ VERTICAL HORIZ NO. NO. BLOWBACK BLOWBACK FORMAT MODE SPACING SPACING ROW COL RATIO % FULL __________________________________________________________________________ 2463 CINE 12.5 mm 15.5 mm 7 9 17 70 2060 COMIC 16.5 11.75 5 12 18 90 2498 COMIC 12.5 10 7 14 21.5 90 42208 CINE 7 8.75 14 16 30 70 42325 COMIC 7 5.5 13 25 38 90 48270 CINE 6.25 7 15 18 34 70 48420 COMIC 6.25 5 15 28 43 90 __________________________________________________________________________
The CINE mode produces sequential pages along a column top to bottom, and the COMIC mode produces sequential pages along a row left to right. The first two numbers of the format indicate the magnification needed for full blowback and the remaining numbers indicate the number of frames. Thus, format 2498 is magnified by 24 power, and it contains 98 frames. By blowing back less than 100%, the machine compensates for positional inaccuracies and for failure for the frame size to have dimensions exactly proportional to the 81/2 in.times.11 in (216 mm.times.279.4 mm) copy.
If an automatic reader printer is designed for multiple format microfiche, certain problems are created. The first relates to indexing. If frames are of different sizes, then corresponding frame indexes will yield different positions on different format microfiche. For example, in format 2060, a command to index to the fifth row and twelfth column would index the machine to the frame at the lower right corner of the microfiche. If format 48420 were used, the same command directs the reader printer to a frame near the middle of the microfiche.
Multiple format readers have been previously provided. One such reader is the Bruning Model 97 reader manufactured by the assignee herein. It has two lenses for different magnifications, and switching from one lens to the other modifies the controller to compensate for the different frame locations on different format microfiche. In the Model 97, switching between the two lenses modifies the control circuit which controls the motors which drive the platen to the correct location. The Model 97 is not a printer, however, and printing creates its own set of problems.
The problems are minimal if printing is done on a stationary photoreceptive medium with the image of the entire frame being projected to the entire stationary photoreceptive medium. However, such copiers are inherently slow, and a higher speed copier requires scanning of the frame and projecting the scanned portion to a moving photoreceptive medium. The immediately adjacent frame areas are projected to immediately adjacent areas on the photoreceptive surface so that the entire frame is ultimately projected to the moving photoreceptive medium. The present invention uses a rotating xerographic drum, but xerographic or photographic belts could also be used.
There must be coordination between the movement of the frame in the path of the light and the rotation of the xerographic drum. New formats change the relationship. For example, with format 2060 microfiche, the frame must be scanned horizontally 11.75 mm each time the xerographic drum rotates once, but the horizontal scan of format 48420 is only 5 mm. Therefore, unless the horizontal scanning speed of the frame of microfiche is modified with respect to the rotation of the xerographic drum, the copying will be incorrect.
Another problem relates to maintaining constant velocity during scanning. Stepper motors, which are used to drive the platen holding the microfiche, do not have constant velocity drive between steps. Certain prior art devices use synchronous motors to drive the platen during scanning. As successive windings are energized, the torque on the rotor varies as the rotor moves between winding. This produces a somewhat jerky motion for the platen. Although these jerks are small, they result in unclear copies.
The stepper motor also has difficulty accelerating the platen. If the scan starts at the beginning of a frame, the platen will be moving at an increasing velocity at the beginning of the frame, have constant velocity over the center of the frame and moving at decreasing velocity at the end of the frame.
Other problems relate to the magnification itself. Formats of different magnifications will need lenses of different magnifications, and the chosen lens will have to be moved into and out of the light path. Because of the high degree of magnification required, there is an extremely small depth of focus. Therefore, the distance from the film plane to the focused lens must remain constant as the machine moves from frame to frame. If not, as the machine automatically proceeded from the lower right frame to the upper left frame, the images of certain frames may be out of focus. Because such machines are intended to be substantially automatic, the operator cannot continually check on the focus of intermediate frames. The problems are greater with multiple lenses because the play necessary to allow movement of different lenses into the light path may create inaccuracies in positioning the lens.
In the prior art, one of the ways of maintaining the position of the lens with respect to the film surface was to carry the lens in a brass holder and rest the holder on the glass platen. Moving the platen beneath the lens, therefore, would not affect the distance from the microfiche to the focused lens. Resting the brass covers on the platen creates problems. In the present invention, the printer is below the platen so that the lenses must be mounted below the platen. The brass can also scratch the glass platen.
Simplicity of operation is also a concern. It is more complicated, for example, to require an operator to choose a particular lens for the format and then to have the operator also be required to set controls corresponding to the format for scan rate and indexing. Ideally, the machine would automatically switch indexing and scan when a new lens is chosen.
Focusing is also a concern. Each time a lens is chosen, it will have to be focused, and it is preferable to do the focusing mechanically rather than manually. The normal way of focusing these lenses is to merely move them toward or away from the film plane. Such movement can be accomplished by gears tied into motors.
It is uneconomical, however, to have a motor for each lens, and it is desirable to have a single motor focus all lenses. Because the focus of the lenses that are not being immediately used is unimportant, the focusing motor can move all three lenses simultaneously until the lens being used is in focus. Positive drive between the lenses and the motor is not desirable. if the lens reaches its fullest travel, the lens will stop the motor. In order to avoid damage to the motor, an expensive clutch may be necessary. Separate controls will also be required. Therefore, it would be desirable if continued motor rotation reciprocated the lens.
Microfiche is produced in standard formats, but careless operators and worn machines can produce microfiche that does not conform to specifications. For example, assume that in one format having 10 frames in the y direction the nominal distance between outermost frames is 140 mm. If the platen has positioned one of the outermost frames in the light path, a command to move 140 mm in the y direction would position the other outermost frame in the light path. Actually, in the present invention, the command would be to move a certain number of steps, and the distance between outermost frames would be stored as a number of steps.
If the outermost frames are only 135 mm apart, if the first frame is aligned, a command to move to the other frame will result in missing the frame by 5 mm. In slower reader printers where each frame is viewed before printing, and the operator centers each image before printing, the problem is avoided, but where printing of frames are automatically sequenced, the operator offers little or no manual control.
The alignment problem is further complicated if the rows in the COMIC mode or columns in the CINE mode are skewed. In the COMIC mode, if movement along the y axis does not have compensating x correction, each successive frame will be incorrectly positioned either upward or downward.
As was previously stated, the object of the present invention is to disclose and provide a reader printer and a method of reading and printing microfiche that solves many of the problems of the prior art. In the foregoing description, a number of other problems are also mentioned, and it is an object to this invention to disclose and provide a reader printer that solves the problems.